﻿// This code is released under the BSD license.
namespace PugLib.Filters
{
    using System;
    using System.Linq;
    using System.Linq.Expressions;

    public static class PredicateBuilder
    {
        public static Expression<Func<T, bool>> True<T>()
        {
            return f => true;
        }

        public static Expression<Func<T, bool>> False<T>()
        {
            return f => false;
        }

        public static Expression<Func<T, bool>> NotNull<T>()
        {
            return f => (null != f);
        }


        public static Expression<Func<T, bool>> Or<T>(this LambdaExpression expr1, Expression expr2)
        {
            InvocationExpression invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
            return Expression.Lambda<Func<T, bool>>(Expression.Or(expr1.Body, invokedExpr), expr1.Parameters);
        }


        public static Expression<Func<T, bool>> And<T>(this LambdaExpression expr1, Expression expr2)
        {
            InvocationExpression invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
            return Expression.Lambda<Func<T, bool>>(Expression.And(expr1.Body, invokedExpr), expr1.Parameters);
        }
    }
}